Age-hardening behaviour of two metastable beta-titanium alloys

Ng, Hoi-Pang; Douguet, Elodie; Bettles, Colleen Joyce; Muddle, Barrington Charles

doi:10.1016/j.msea.2010.07.055

Cited by 55 publications

(14 citation statements)

References 19 publications

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“…Nag [47] that in case of the same alloy Ti-10V-2Cu, water quenched condition results in athermal ω phase with 3 nm, and 272 HV in hardness, but air cooled condition results in athermal ω phase with 24 nm, and 507 HV in hardness instead. On the other hand, water quenched Ti-10V-2Ni alloy results in athermal ω phase with 6 ~ 12 nm, and 375 HV in hardness.…”

Section: Discussionmentioning

confidence: 93%

Microstructural evolution and age hardening behavior of a new metastable beta Ti–2Al–9.2Mo–2Fe alloy

et al. 2015

Materials Science and Engineering: A

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Section: Discussionmentioning

confidence: 93%

Microstructural evolution and age hardening behavior of a new metastable beta Ti–2Al–9.2Mo–2Fe alloy

et al. 2015

Materials Science and Engineering: A

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“…Improved atomic column resolution and contrast have been achieved by sampling only the incoherently scattered electrons using a high angle annular detector in a scanning-TEM (STEM) [5,13,14]. Recently, interest in the omega phase and its effect on subsequent phase transformations [15][16][17][18][19][20][21] have led to new observations through high angle annular dark field (HAADF) imaging [13,[22][23][24].In HAADF images of Ti-5Al-5Mo-5V-3Cr (wt.%), intensity variations have been observed, with the collapsing planes exhibiting a lower intensity than the non-collapsing planes [24]. This intensity difference has been attributed to variations in the average atomic number of each column of atoms, suggesting preferential site occupation and, possibly, ordering within the omega phase.…”

mentioning

confidence: 99%

On the nature of the omega tri-layer periodicity in rapidly cooled Ti-15Mo

et al. 2015

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Scanning/transmission electron microscopy (STEM) High angle annular dark field (HAADF) Electron energy loss spectroscopy (EELS) a b s t r a c t High angle annular dark field (HAADF) images of the omega phase in metastable beta titanium alloys exhibit tri-layered periodicity. However, it is unclear if this indicates preferential site occupation, or is related to the structural modification of omega formation. Here, the periodicity was studied using a combination of HAADF imaging and electron energy loss spectroscopy. The results show that there is no preferential site occupancy or ordering and that the observed intensity variations are related to the imaging conditions.Additions of transition metal elements to titanium are known to stabilise the high temperature beta phase, enabling its metastable retention at room temperature following rapid cooling. However, such material is often reported to contain the omega phase, which forms through the collapse of consecutive pairs of {1 1 1} b [1-3]. This formation mechanism suggests that the parent beta phase has a soft phonon mode with respect to {1 1 2} b shear [4], and that the omega phase present following rapid cooling should be compositionally indistinct from the parent matrix at the point of quenching. However, there is evidence to suggest that a chemical alteration accompanies the structural modification [5,6]. Thus, determining the mechanism of omega formation remains an intriguing question.The nature of the omega transformation has been studied extensively through lattice imaging using a transmission electron microscope (TEM) [7][8][9][10][11][12]. However, phase contrast effects prevented early studies from directly imaging the {1 1 1} b collapse and compositional information was unobtainable due to the dominance of elastically scattered electrons [13]. Improved atomic column resolution and contrast have been achieved by sampling only the incoherently scattered electrons using a high angle annular detector in a scanning-TEM (STEM) [5,13,14]. Recently, interest in the omega phase and its effect on subsequent phase transformations [15][16][17][18][19][20][21] have led to new observations through high angle annular dark field (HAADF) imaging [13,[22][23][24].In HAADF images of Ti-5Al-5Mo-5V-3Cr (wt.%), intensity variations have been observed, with the collapsing planes exhibiting a lower intensity than the non-collapsing planes [24]. This intensity difference has been attributed to variations in the average atomic number of each column of atoms, suggesting preferential site occupation and, possibly, ordering within the omega phase. Intensity variations between the collapsing and non-collapsing planes have also been observed in rapidly cooled Ti-18Mo (wt.%) [13]. Similarly, tri-layered structures have been reported in HAADF images of Gum metal (Ti-31.9Nb-2.0Ta-2.7Zr-0.3O wt.%) [22]. However, multi-slice scattering simulations suggest that the observed intensity variations could also be related to the structural modification of the omega phase rather than compositio...

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“…Another important negative factor in thermal wear is the oxidation at the tip of the thermal cracks. The oxidation at the crack tip always aggravates the stress condition and speeds up the occurrence of thermal cracks [35,36]. Therefore, the alloying of elements with more affinity for oxygen than that of iron is likely to result in the formation of oxides and other non-metallic compounds.…”

Section: Energy Dispersive X-ray Spectroscopy (Edxs) Analysismentioning

confidence: 99%

“…The areas with crack density and cracks at their highest and deepest values recorded the lowest hardness values [28]. At temperatures of about 500 • C, the hardness value of the materials was minimized and declined considerably at high temperatures [35,36]. At above 500 • C, Cr, Mo, and V carbides hardened, and steadily decreased the material's hardness [28].…”

Section: Hardness Propertiesmentioning

confidence: 99%

Thermally-Induced Crack Evaluation in H13 Tool Steel

Abdulhadi

Ahmad

Ismail

et al. 2017

Metals

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This study reported the effect of thermal wear on cylindrical tool steel (AISI H13) under aluminum die-casting conditions. The AISIH13 steels were immersed in the molten aluminum alloy at 700 • C before water-quenching at room temperature. The process involved an alternating heating and cooling of each sample for a period of 24 s. The design of the immersion test apparatus stylistically simulated aluminum alloy dies casting conditions. The testing phase was performed at 1850, 3000, and 5000 cycles. The samples were subjected to visual inspection after each phase of testing, before being examined for metallographic studies, surface crack measurement, and hardness characteristics. Furthermore, the samples were segmented and examined under optical and Scanning Electron Microscopy (SEM). The areas around the crack zones were additionally examined under Energy Dispersive X-ray Spectroscopy (EDXS). The crack's maximum length and Vickers hardness profiles were obtained; and from the metallographic study, an increase in the number of cycles during the testing phase resulted in an increase in the surface crack formation; suggesting an increase in the thermal stress at higher cycle numbers. The crack length of Region I (spherically shaped) was about 47 to 127 µm, with a high oxygen content that was analyzed within 140 µm from the surface of the sample. At 700 • C, there is a formation of aluminum oxides, which was in contact with the surface of the H13 sample. These stresses propagate the thermal wear crack length into the tool material of spherically shaped Region I and cylindrically shape Region II, while hardness parameters presented a different observation. The crack length of Region I was about 32% higher than the crack length of Region II.

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Age-hardening behaviour of two metastable beta-titanium alloys

Cited by 55 publications

References 19 publications

Microstructural evolution and age hardening behavior of a new metastable beta Ti–2Al–9.2Mo–2Fe alloy

Microstructural evolution and age hardening behavior of a new metastable beta Ti–2Al–9.2Mo–2Fe alloy

On the nature of the omega tri-layer periodicity in rapidly cooled Ti-15Mo

Thermally-Induced Crack Evaluation in H13 Tool Steel

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